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Molecular Basis for SMC Rod Formation and Its Dissolution upon DNA Binding

Soh, Young-Min, Bürmann, Frank, Shin, Ho-Chul, Oda, Takashi, Jin, Kyeong Sik, Toseland, Christopher P., Kim, Cheolhee, Lee, Hansol, Kim, Soo Jin, Kong, Min-Seok, Durand-Diebold, Marie-Laure, Kim, Yeon-Gil, Kim, Ho Min, Lee, Nam Ki, Sato, Mamoru, Oh, Byung-Ha, Gruber, Stephan
Molecular cell 2015 v.57 pp. 290-303
DNA, chromosomes, dimerization
SMC condensin complexes are central modulators of chromosome superstructure in all branches of life. Their SMC subunits form a long intramolecular coiled coil, which connects a constitutive “hinge” dimerization domain with an ATP-regulated “head” dimerization module. Here, we address the structural arrangement of the long coiled coils in SMC complexes. We unequivocally show that prokaryotic Smc-ScpAB, eukaryotic condensin, and possibly also cohesin form rod-like structures, with their coiled coils being closely juxtaposed and accurately anchored to the hinge. Upon ATP-induced binding of DNA to the hinge, however, Smc switches to a more open configuration. Our data suggest that a long-distance structural transition is transmitted from the Smc head domains to regulate Smc-ScpAB’s association with DNA. These findings uncover a conserved architectural theme in SMC complexes, provide a mechanistic basis for Smc’s dynamic engagement with chromosomes, and offer a molecular explanation for defects in Cornelia de Lange syndrome.